Aggregation cause timeout issue

here are some new comments we found as it happen again.
[pool www] pid 30 script_filename = /code/web//index.php [0x00007f1a27016b30] rename() /code/web/core/lib/Drupal/Core/File/FileSystem.php:391 [0x00007f1a27016a40] move() /code/web/core/lib/Drupal/Core/File/FileSystem.php:512 [0x00007f1a27016970] saveData() /code/web/modules/contrib/advagg/src/Asset/AssetOptimizer.php:291 [0x00007f1a27016870] writeFile() /code/web/modules/contrib/advagg/src/Asset/CssOptimizer.php:99 [0x00007f1a270167a0] optimizeFile() /code/web/modules/contrib/advagg/src/Asset/AssetOptimizer.php:255 [0x00007f1a270166e0] scanFile() /code/web/modules/contrib/advagg/src/Asset/AssetOptimizer.php:169 [0x00007f1a270165e0] processAssetArray() /code/web/modules/contrib/advagg/advagg.module:114 [0x00007f1a27016540] advagg_css_alter() /code/web/core/lib/Drupal/Core/Extension/ModuleHandler.php:562 [0x00007f1a270163e0] alter() /code/web/core/lib/Drupal/Core/Asset/AssetResolver.php:159 [0x00007f1a27016260] getCssAssets() /code/web/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php:311 [0x00007f1a27016090] processAssetLibraries() /code/web/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php:157 [0x00007f1a27015fa0] processAttachments() /code/web/core/modules/big_pipe/src/Render/BigPipeResponseAttachmentsProcessor.php:94 [0x00007f1a27015ec0] processAttachments() /code/web/core/lib/Drupal/Core/EventSubscriber/HtmlResponseSubscriber.php:45 [0x00007f1a27015dc0] onRespond() /code/web/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php:142 [0x00007f1a27015d30] call_user_func() /code/web/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php:142 [0x00007f1a27015c10] dispatch() /code/vendor/symfony/http-kernel/HttpKernel.php:202 [0x00007f1a27015b60] filterResponse() /code/vendor/symfony/http-kernel/HttpKernel.php:190 [0x00007f1a27015a80] handleRaw() /code/vendor/symfony/http-kernel/HttpKernel.php:81 [0x00007f1a270159b0] handle() /code/web/core/lib/Drupal/Core/StackMiddleware/Session.php:58 [0x00007f1a270158f0] handle() /code/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php:48
It looks like big_pipe and advagg_css_alter() are two that slow down and trigger the timeout error.